The process of needling in a needling machine brings about the consolidation of a fiber fleece web being transported continuously through the needling machine. When the needle bar executes only a movement directed perpendicularly to the direction in which the fiber fleece web is moving, the forward movement of the continuously transported fiber fleece web is slowed by the needles during the phase of the needling cycle in which the needles are engaged in the fiber fleece web. This results in an undesirable distortion of the fiber fleece and to the cyclical occurrence of an elastic bending of the needles.
As a remedy for these disadvantageous effects, in U.S. Pat. No. 5,732,453 a second drive is assigned to the needle bar, which makes the needle bar oscillate parallel to the fiber fleece web (horizontal movement) cyclically and in synchrony with the stitching movement perpendicular to the fiber fleece (vertical movement). This horizontal movement proceeds in and opposite to the transport direction of the fiber fleece web through the needling machine. The timing of the horizontal movement is superimposed on the vertical stitching movement of the needle bar in such a way that, during the phase of each movement cycle in which the needles are engaged in the fiber fleece, the movement of the needle bar in the horizontal direction follows the forward movement of the fiber fleece through the needling machine, whereas, in the state in which the needles are disengaged from the fleece, the needle bar returns in the horizontal direction back to the starting position. When viewed from the side, transversely to the transport direction of the fiber fleece web, therefore, the needle bar executes a gyrating movement, which is more-or-less circular or elliptical depending on the ratio between the horizontal stroke and the vertical stroke.
As a further improvement to this solution, a mechanical attachment is proposed in U.S. Pat. No. 6,161,269, by means of which the horizontal movement of the needle bar is easily adjustable in small increments, preferably in a continuously variable fashion.
Common to all of the approaches described above is that the vertical movement and the horizontal movement of the needle bar are synchronized with each other. In other words, the needle bar moves up and down in the vertical direction precisely during the period in which the needle bar is moving back and forth in the horizontal direction.
It is an object of the present invention to provide a method for actuating a needle bar in a needling machine by means of which the fiber fleece can be transported through the needling machine at a higher speed and/or by means of which a larger number of stitches can be produced in the fiber fleece.